When president Obama decided to release the Bush-era Justice Department's interrogation memos last month, he tried to calm an anxious CIA by publicly declaring that operatives who "reasonably" relied on them would not face criminal prosecution. But agency officials still have plenty to worry about. Despite Obama's assurances, a Justice Department special counsel is quietly ratcheting up his probe into a closely related subject: the CIA's destruction of hundreds of hours of videotape showing the waterboarding of two high-value Qaeda suspects. At the same time, a Senate panel is planning the first public hearing dealing with CIA interrogations, including testimony from a star witness: Ali Soufan, the former FBI agent who vigorously protested the questioning of one of the detainees, terror suspect Abu Zubaydah.